Cheng-Hsing Chen

The Taiwan High Speed Rail (THSR) passes through the Southern Taiwan Science Park (STSP) where the high-tech fabs inside are very sensitive to ground vibrations. In order to characterize the attenuation of ground vibration with distance in STSP, a series of small-scale in-situ vibration tests were conducted at STSP sites before the operation of THSR. The tests include falling weight tests and shaking tests which were performed on the ground surface, on shallow foundation, and on prototype pile foundation. For falling weight tests, hammer weights of 80, 120, 220, 260, 430 kN and drop heights of 0.5 m—3.0 m were adopted to generate different levels of ground vibration. For shaking tests, exciters that can generate harmonic loads up to 100 or 200 kN were used for ground vibration tests. For all tests, the ground vibrations at various distances were monitored to deduce the associated attenuation coefficients. In this paper, results of all falling weight tests and shaking tests are summarized and compared with those of in-situ measurements of ground vibrations induced by the test runs of THSR trains. Conclusions show that the results of small-scale falling weight vibration tests can be used to predict the decay of ground vibration induced by the operation of high speed trains.

The exposure of bridge foundations due to scouring has been recognized as the most critical cause for highway bridge failures in Taiwan, yet difficulties have been found to identify its risk level. In an effort to develop an efficient measure for the detection and estimation of the scour of bridge foundations, a series of field vibration measurements were conducted on selected highway bridges of which the foundations had been suffered different levels of scouring. In this paper, theoretical background of utilizing vibration measurement to estimate the exposure of bridge foundation is introduced. The setup of vibration measurement on bridges and schemes of data processing are described. Results of the mentioned field tests on bridges are presented, and the feasibility of using vibration measurement to evaluate the scour of bridge foundations is thus verified. The findings of this study are helpful in developing the inspection and monitoring technology for bridge scouring.

The capacity of a pile-soil system can be obtained by pushover analysis using the beam-on-nonlinear-Winkler foundation model. When the pile section enters the plastic state, the plastic hinge method is usually adopted to model its postyielding flexural behavior. The propagation of the plastic zone in a pile can be traced using a series of plastic hinges distributed along the pile that is embedded in the soil. This study proposes a proper model for arranging the distributed plastic hinges along the depths of the pile that are prone to yielding. A modified definition of plastic curvature is proposed herein in order to correctly simulate the nonlinear flexural behavior of a pile. Examples are presented to show the effectiveness of the proposed model.

In order to characterize the ground vibration attenuation with distance in Southern Taiwan Science Park (STSP), a series of small-scaled in-situ vibration tests, including falling weight tests and shaking tests, were conducted by National Center for Research on Earthquake Engineering (NCREE) at sites in STSP where Taiwan High Speed Rail (THSR) passes through. Those tests were performed on the ground surface, on shallow foundation, and on proto-type pile foundation. For falling weight tests, hammer weights of 8, 12, 22, 26, 43 metric tons and drop heights of 0.5m∼3.5m were adopted to generate different levels of ground vibration. The decay of ground vibrations with respect to distance was monitored to deduce attenuation coefficient. In this paper, results of all the falling weight tests are summarized and compared with those of in-situ measurements of ground vibrations excited by test runs of THSR trains. Conclusions show that the attenuation coefficients of ground vibration deduced from the falling weight tests present a similar trend to, but with larger values than, those deduced from measurements of test runs of THSR, and therefore can be used to predict the decay of ground vibrations induced by the operation of high-speed trains.